System and method for horizontal directional drilling and product pulling through a pilot bore

ABSTRACT

Disclosed is a system and method employed in a horizontal directional drilling (“HDD”) process. An exemplary embodiment includes a drill bit with thirteen (13) or more splines for improved orientation of the drill bit relative to the orientation of a bent sub. Another exemplary embodiment includes a drill bit configured for receipt of a pulling device so that the drill bit may be used in a back reaming step to pull a product back through a pilot bore. Another exemplary embodiment includes a pulling device for mounting to a drill bit. The pulling device, in some embodiments, may include one or more pins for diverting and channeling air and/or fluid through the drill bit to lubricate a hammer assembly and/or the product being pulled as the drill string to which the drill bit is attached is retracted back through the pilot bore.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application for patent claims priority under 35 U.S.C. §119(e) to,and incorporates by reference the entire contents of, U.S. provisionalapplication entitled “SYSTEM AND METHOD FOR HORIZONTAL DIRECTIONALDRILLING AND PRODUCT PULLING THROUGH A PILOT BORE,” filed on Mar. 14,2013 and assigned application Ser. No. 61/781,211.

BACKGROUND

The present invention relates to horizontal directional drilling (“HDD”)and, more particularly, to improved drill bits and improved pullingsystems to be used in HDD processes.

Horizontal directional drilling (“HDD”), also termed “slant drilling,”is the practice of drilling non-vertical bores. A common application forHDD is for the installation of utility products such as undergroundwiring, small bore piping, cable bundles, and the like. The HDD processtypically begins with drilling a pilot bore along a desired undergroundpath. Next, the pilot hole is enlarged to a desired diameter and itswalls conditioned by passing a larger cutting tool, sometimes termed a“back reamer,” back through the pilot hole. As one of ordinary skill inthe art understands, selection of a back reamer may depend on theproduct that will ultimately be installed in the bore. Finally, theproduct is installed in the enlarged hole by way of being pulled behindthe reamer as the drill string is retracted from the reamed bore.

An HDD process may include the use of a viscous fluid known as drillingfluid. Drilling fluid is typically a mixture of water and eitherbentonite or a polymer that is continuously pumped to the drill bitlocated at the very end of a drill string in the down-the-hole (“DTH”)assembly. The drilling fluid is blown through ports in the drill bit tofacilitate the removal of cuttings, stabilize the bore hole, cool thedrill bit cutting head, and lubricate the passage of the product. Thedrilling fluid may be recycled through a machine called a reclaimerwhich removes the drill cuttings and maintains the proper viscosity ofthe fluid. Advantageously, drilling fluids hold the cuttings insuspension to prevent them from clogging the bore, thereby alleviatingpressure on the drill bit that could slow the boring process.

BRIEF SUMMARY OF THE INVENTION

Various embodiments, aspects and features of the present inventionencompass a system and/or a method employed in a horizontal directionaldrilling (“HDD”) process.

An exemplary embodiment includes a drill bit with thirteen (13) or moresplines for improved orientation of the drill bit relative to theorientation of a bent sub.

Another exemplary embodiment includes a drill bit configured for receiptof a pulling device so that the drill bit may be used in a back reamingstep to pull a product back through a pilot bore.

Another exemplary embodiment includes a pulling device for mounting to adrill bit. The pulling device, in some embodiments, may include one ormore pins for diverting and channeling air and/or fluid through thedrill bit to lubricate a hammer assembly and/or the product being pulledas the drill string to which the drill bit is attached is retracted backthrough the pilot bore.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIGS. 1A-1B depict a method for aligning or “clocking” the orientationof a drill bit relative to the orientation of a bent sub.

FIG. 2 depicts an exemplary embodiment of a drill bit with thirteensplines.

FIGS. 3A-3B is a non-limiting example of a drill bit and pulling device,according to an embodiment of the invention.

FIG. 4 is a non-limiting example of a blow hole pin that may be includedin some embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments and aspects of the present invention provide solutions tovarious needs in the art by providing a drill bit with thirteen (13) ormore splines. Further embodiments and aspects of the present inventionprovide solutions to various needs in the art by providing a drill bitand pulling system for converting a drill bit to a back reamer suitablefor pulling product back through a pilot bore.

A typical DTH drill assembly is screwed onto the bottom of the drillstring and may include any number of components including, but notnecessarily limited to, a sonde assembly, a bent sub, a hydraulic motorassembly, a chuck and a drill bit.

The sonde assembly may include various instrumentation and transmittersfor measuring various data such as angle of the string, rotation,direction of the bore, temperature and the like. The data measured bythe sonde assembly is transmitted to the surface and used to adjust thedrilling direction, as is understood by one of ordinary skill in theart. Location and guidance of the drilling is an important part of thedrilling operation, as the drill bit is under the ground while drillingand, in most cases, not visible from the ground surface. Uncontrolled orunguided drilling can lead to substantial destruction, which can beeliminated by properly locating and guiding the drill bit.

The sonde assembly provides the means by which the drill bit may belocated and guided through use of a “walk-over” locating system. Thedata collected by the sonde assembly is encoded into an electro-magneticsignal and transmitted through the ground to the surface to be receivedby the walk-over system. At the surface, when a receiver (usually ahand-held locator) is positioned over the sonde, the signal is decodedand steering directions are subsequently relayed to the bore machineoperator.

The bent sub portion of the DTH assembly, sometimes termed theadjustable kickoff sub, is a small segment of the drill string with abody portion that is bent at an angle rather than being straight. Insome embodiments of a DTH assembly, the bent sub may be located abovethe drill bit and below the motor assembly, although such is notrequired in all embodiments of a DTH assembly. As one of ordinary skillin the art recognizes, the inclusion of a bent sub in the drill stringmakes it possible to steer the bore as needed by pushing off the side ofthe bore to produce a sideways force on the drill bit. The specific bendangle of a bent sub is application specific, as one of ordinary skill inthe art understands. An exemplary bent sub, however, may include a lowerthread portion that is inclined 1°-3° from the axis of the bent subbody.

The hydraulic motor, chuck and drill bit components of a DTH assemblywork together to operate like a mini jackhammer that breaks hard rockinto small flakes and dust. The debris of flakes and dust issubsequently blown clear of the drill bit by exhausted air. Thepercussion mechanism, i.e. the hydraulic motor, is located directlybehind the drill bit. The pipes that form the drill string transmit thenecessary feed force and rotation to hydraulic motor and drill bit aswell as the compressed air and/or drilling fluid. As understood by oneof ordinary skill in the art, the drill pipes are added to the drillstring successively behind the DTH assembly as the bore is drilled. Apiston in the hydraulic motor strikes the impact surface of the drillbit directly, while the bent sub and hydraulic motor casing worktogether to provide straight and stable guidance of the drill bit.Advantageously, the impact energy generated in a DTH does not have topass through the joints of the drill string and, as such, energy is notlost in the various joints.

Once the pilot bore is completed in an HDD process, the pilot bore isback reamed. In the back reaming step of a HDD process, the pilot boremay be expanded to a desired diameter and the walls of the boreconditioned for receipt of a product. Back reaming is a part of almostevery horizontal directional drilling operation. Typically, to begin theback reaming step, the DTH assembly, or some portion of the DTHassembly, must be decoupled from the drill string so that a back reamingtool may be attached in its place. As described above, the back reamingtool may be pulled back through the pilot bore to enlarge the bore andcondition its walls. In many HDD operations, the product to be installedmay be pulled back through the bore during the back reaming step byattaching the product to a swivel which is mounted to the back reamertool.

Current systems and methods for horizontal directional drilling are inneed of improvement. Returning to the pilot boring step in an HDDprocess, for example, the accuracy at which the DTH assembly may besteered is not just dependent on the data taken from the sonde assemblybut also the accuracy at which the various components of the DTH areconnected (i.e., “clocked”) relative to one another.

In current HDD systems and methods, one or more sensor/transmitterinstruments in the sonde housing is/are orientated relative to the bentsub. As described above, a hydraulic motor (i.e., a “hammer”) isattached to the opposite end of the bent sub. On the opposite side ofthe hammer from the bent sub, a “slant bit” drill bit is clockedrelative to the orientation of the bent sub. Notably, the accuracy atwhich the drill bit is positioned relative to the bent sub directlyaffects the steering accuracy during the HDD process.

Current drill bits used in HDD systems and methods include 12 or lesssplines. Notably, because the number of splines on current drill bits isinadequate to accurately clock the orientation of the drill bit on oneend of a hammer to the orientation of a bent sub on the other end of thehammer, shims inserted between the chuck and the hammer are often usedas spacers to accommodate any misalignment. As one of ordinary skill inthe art understands, the use of spacer shims to make up for theinaccuracy at which a drill bit that includes 12 or less splines can beclocked to a bent sub in a DTH assembly can be a tedious and timeconsuming task because the drill bit must be repeatedly removed,replaced and measured relative to the bent sub until the correct amountof shims is determined.

As one of ordinary skill in the art understands, orientation of a drillbit to a bent sub is critical in an HDD process for at least the reasonthat the sonde sensor/transmitter instrument is clocked to the bent suband provides data back to the surface that is used to steer the DTHassembly. Notably, therefore, if the drill bit is not accurately clockedto the bent sub, the data associated with the bent sub that is collectedby the sonde will not be an accurate representation of the direction atwhich the drill bit is moving. For example, in a typical HDD process,the information transmitted by the sonde is represented by a “clock”such that “12 o'clock” represents vertically upward, “3 o'clock”represents a right direction, “6 o'clock” represents a downwarddirection, and “9 o'clock” represents a left direction. In the exemplarysystem, one of ordinary skill in the art understands that “1 o'clock”represents an upward direction and slightly to the right. Notably, otherinformation measured and transmitted by the sonde may include, but isnot limited to including, information representative of relative depth,temperature, battery strength, signal strength, pitch and the like.

Returning to the exemplary application of an HDD process, a typical borelength may be 600 feet in distance. If the drill bit is inaccuratelyclocked relative to the bent sub, the steering of the DTH assembly overthe 600 foot length of the bore may be unpredictable and in need ofcounter steering. For example, while the sonde is transmitting datameasured relative to the bent sub that indicates that the bore directionis at 12 o'clock, the inaccuracy at which the drill bit was clocked tothe bent sub may be causing the bore direction to actually be moreconsistent with 1 o'clock. In such a situation, over the 600 foot borethe direction may deviate to the right off of the desired path. Toaccommodate the misalignment in the exemplary application, the operatorof the HDD system must essentially steer back to the left as if thedesired bore direction were 9 o'clock , all the while recognizing thatthe actual drilling direction (because of the misalignment of the bit tothe bent sub) is closer to 10 o'clock in order to overcome thedirectional deviation of the bore.

What is needed in the art, therefore, is a drill bit having thirteen(13) or more splines so that the drill bit may be accurately clocked inits position relative to a bent sub orientation. Advantageously, byincluding 13 or more splines on a drill bit, the need for shims may bereduced or alleviated as the resolution of the positioning of the drillbit relative to a bent sub orientation may be improved to such an extentthat directional data associated with the bent sub (and collected by asonde) may be used to steer a DTH assembly without significant countersteering.

Current systems and methods for horizontal directional drilling are alsoin need of improvement in the step of installing product through a bore.As described above, hammers and drill bits used in DTH assemblies forinstalling products of the utility industry must be removed from thedrill string and replaced with a back reamer. To break the hammer (anddrill bit) off the drill string to attach the back reamer may requirethe use of a back hoe, oil field tongs or other heavy piece ofmachinery. In some applications, the back reamer may include a swivelfor attaching the product and “pulling” the product back through thebore during the back reaming step (the swivel prevents the product fromrotating with the drill string during the back reaming step). Inaddition to pulling the product back through the bore, a back reamer mayalso be configured to mix fluid with the cuttings and lubricate theproduct.

What is needed in the art is a system and method for pulling productback through a pilot bore without having to replace the DTH assemblywith a back reamer device. An embodiment of the invention is a pullingdevice configured to attach to a drill bit in the field at the exit pitof a pilot bore, thereby alleviating the need to replace the DTHassembly with a back reamer. Essentially, by attaching a pulling deviceaccording to an embodiment of the invention to a drill bit configured toreceive the pulling device, the drill bit is converted to a back reamersuitable for pulling product sized to fit within the pilot bore.

An exemplary embodiment of a pulling device includes a plate componentthat covers the blow holes of the drill bit and a pair of bolts or pinsthat extend through the plate into the blow holes. Advantageously, theblow hole pins of the exemplary embodiment may divert drilling fluid andair forward of the drill bit as it is pulled back through the bore tolubricate the product being pulled. The diverted fluid and/or air mayalso lubricate the hammer assembly during the back boring step. Anexemplary blow hole pin that is included in a given embodiment of apulling device may include four keyway grooves cut on the outside radiusof the pin from the bottom up toward the threads. Air forced through theblow holes of the drill bit would be diverted by the plate along thechannel on the drill bit and blown back toward the hammer, therebymoving debris and lubricating the hammer as it is being pulled backthrough the bore. Certain embodiments of a blow hole pin may also have ahole drilled through its center so that air and fluid may be allowed topass along toward the product being pulled, thereby lubricating theproduct. In some embodiments, the backside of the plate which mates withthe drill bit may be milled to accommodate the contour of the drill bitincluding any wear buttons. It is further envisioned that certainembodiments may include a pulling eye and/or swivel component forextending from the plate and configured for pulling the product as thedrill string is retracted from the bore.

Systems, devices and methods of the various inventions have beendescribed using descriptions of embodiments thereof that are provided byway of example and are not intended to limit the scope of thedisclosure. The described embodiments comprise different features, notall of which are required in all embodiments. Some embodiments utilizeonly some of the features or possible combinations of the features.Variations of embodiments that are described and embodiments thatcomprise different combinations of features noted in the describedembodiments will occur to persons of the art.

Moreover, it will be appreciated by persons skilled in the art thatsystems, devices and methods of the inventions are not limited by whathas been particularly shown and described herein and above. Therefore,although selected aspects have been illustrated and described in detail,it will be understood that various substitutions and alterations may bemade therein without departing from the spirit and scope of the presentinvention. As such, the scope of the invention is limited only as it maybe defined by a claim.

What is claimed is:
 1. A drill bit for use in a horizontal directionaldrilling system, the drill bit comprising thirteen or more splines.
 2. Asystem for pulling product through a pilot bore drilled by a directionaldrilling system, the system comprising the structures described aboveand illustrated in the drawings.